Please follow the below steps to uninstall Click2Export from your Dynamics 365 CRM environment.
Step 1: Remove Click2Export assembly from your workflows.
If you’ve used Click2Export assembly in your workflow, remove the assembly from your workflow.
If you are not using Click2Export assembly, then start from Step 2.
Step 2: Navigate to Settings -> Solution -> Select Click2Export solution
Step 3: Click on delete button.
Step 4: Click on OK button.
After clicking on OK your solution will be successfully uninstalled.